C L A I M S
1. "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT" constituents of a set of pieces of equipment that partly integrates itself to the blast furnace iron notch (1) and a part of it is auxiliary in its concrete placement and it is removable, aimed to produce the concrete placement of the iron notch (1) of high duration and of a high work security level characterized by being preferably built with steel plate with measures that comply with the iron notch (1) and by being constituted of the rack (10) with a side profile at a proper angle with the blast furnace metallic furnace shell (4), for coinciding at a straight angle with the drill (6) and the blast-furnace gun (7) and by having shelves (11), pillars (12) and holes (13) and also by being constituted of the auxiliary removable plate (14), with windows (15), bucket (16), angular bend (17) and sealing plates (19). 2. "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT", according to claim 1 , characterized by the fact that the rack (10) integrates the iron notch (1), providing it with a concrete placement perfection and of long duration and the auxiliary removable plate (14) for enabling its fast and safe concrete placement, making the external concrete placement (3) part of the iron notch (1) to be at such an angle with the blast furnace metallic furnace shell (4) that the drill (6) and the blast-furnace gun (7) reach it at a straight angle.
3. "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT", according to claim 1 , characterized by the auxiliary removable plate (14) being fixed in a suitable tentative way in the frontal part of the rack (10) and the refractory concrete being thrown into the bucket (16) and going down gravitationally up to the rack (10) lower part.
4. "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT", according to claim 1 , characterized by the fact that the window (15) allows the .introduction of the vibratory element used for compacting the concrete.
5. "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT", according to claim 1 , characterized by the sealing plates (19) being held by weld in the front of the windows (15). |
"RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT".
Fields of this patent:
- Productivity and safety in blast furnaces. - Iron notches, operation and maintenance.
State of the Art.
Blast furnaces constitute the core of the steel industry. It is in them that the iron oxid ores, granulated or pre-processed to make "sinter", are subjected to the hot chemical reduction process, having the carbon as reagent, and they are turned into a metallic alloy composed of more than 97% of the iron element, called pig iron.
The metallic iron in liquid state, with a temperature of about 1 ,500 Centigrade degrees and that flows from the blast furnaces in the runs, is taken to the other pieces of equipment of the steel plant, which will process it to turn it into steel, that is, a complex alloy of iron and other elements with the fewest contents of sulfur, phosphorus and other contaminants as possible.
We say that the blast furnaces are the core of the steel industry because they supply the raw material to all the subsequent processes.
The modern blast furnaces are located in the center of a complex of peripheral pieces of equipment that are responsible for their high productions and quality; the regenerators increase their thermal economies allowing the air injection through their tuyeres to be done at about 1 ,200 Centigrade degrees, special lances make the coke or charcoal fines (breeze) be injected through their tuyeres in order to rise their thermal performances, they receive sinter rather than the granulated ore, besides a stoichiometric amount of water steam in such a way, due to their geometry, that they use the hydrogen formed as a reducing element.
Nowadays, supported by the technological advances in the last 50 years and by the recent automation support, the blast furnaces are considered to be
near their maximum evolution limit, that is, obtaining improvements in the industrial reduction process for oxidated iron ores is only possible with radical changes of paradigm.
Due to economical matters related to the productivity and to the cost reduction, the blast furnaces must have bigger and bigger production capacities, of about millions of tons/year.
The current operational indices are around 99% of the time and the high productivities reached are also due to the millions of dollars invested in the automation and computerization of the blast furnaces. However, when the costs of each stopped hour are observed, a huge need of innovating the processes and maintenance equipment of the pieces and of the most worn-to-be equipment is noticed so that the stopped hours be reduced.
A blast furnace with a production of 2,800,000 tons per year produces 7,670 tons a day or 320 tons an hour.
For the current prices of US$250.00 per ton of pig iron, there is a theorical production loss of US$80,000 per stopped hour.
Taking the finished products of about US$500.00 per ton into consideration, the production loss per stopped hour is that of US$160,000.00. One should also take into account that when a blast furnace process is interrupted, it is rather slowly than abruptly, previously decreasing the production for several hours and similar timings are necessary for returning to the status of maximum production process.
This means a loss of basic production - despite other systemic losses - of about US$200,000.00 per stopped hour.
However, despite the great technological advances of the blast furnaces and of the peripheral pieces of equipment that support them, those simplest pieces of equipment, such as the pieces of equipment and the concrete placement process of the "iron notch" and many others, have been the same for decades.
Analyses reveal that the maintenance stops, whether programmed or not, of the simplest pieces of equipment which are auxiliaries for the blast furnace work, such as the sealing refractories of the iron notches, are responsible for great losses of their productivities. Thus, the equipment productivity and the operational process improvements, known as "supportive services and equipment to the blast furnace", have been the target of great managing efforts, once their importance is clear in order to reduce the number of stopped hours.
It must be stated that the maintenance services performed in the blast furnaces are carried out in extremely hard conditions, due to the high temperatures near such equipment, due to the restricted conditions of space for movement and correctly anatomic positioning, besides always demanding great physical efforts, as they deal with heavy pieces and tools that are hard to handle; in other words, such tasks take long to be carried out due to the local conditions and for meeting the work security rules.
According to the current State of the Art, the "iron notches" are places which require constant maintenance, for the following reasons:
1st - Lengthy contact of the area with the liquid pig iron: - Although the blast furnaces produce liquid pig iron in a continual process, it gets accumulated in its interior and it is released from it periodically in such timings that they optimize the subsequent processes, that is, its transport, when still liquid, to the steel industry by means of the so-called "hot-metal transfer cars", from these to the steel ladles, from these to the equipments that remove the gases and, finally, to the continuous or non continuous ingot casting. 2nd - Security against accidental ruptures: - The runs may also occur for emergency matters and, eventually, for accidental and unexpected matters, due to the rupture of the refractory concrete of the iron notches, a situation that represents a serious accident as the pig iron, at around 1.500 degrees Centigrade, in these cases, is released over the cold canals - or the wet ones, which is much more serious -, it spills and may reach the people who are, by chance, in the running area, and it may get solidified in the reached
areas with serious problems to be removed when solid, as they make large metallic plates, once the blast furnaces produce around 5 tons per minute.
The way used to prevent the accidental ruptures is by providing the blast furnaces with four iron notches and use them in a changing turns, by using each of them up to a safe level of wear and then leaving it inactive until the next programmed halt for the blast furnace maintenance, while another of the four notches is utilized.
3rd - The need to bear temperature and pressure: - As the blast furnaces usually operate at a pressure of about 3,5 Bar in their lower parts, if there is an accidental rupture of the iron notch, this is thrown to the exterior with a great violence and it characterizes a serious accident; thus, the iron notch cores are sealed with refractories and one iron notch is left inactive as soon as it presents a sign of wear in the concrete and this is strictly complied with for security matters. 4th - Operational wear: - The regular wear of the iron notch core comes from the three following reasons and they are part of the operational system of the blast furnaces: a - the wear of the refractories caused by the passage, under pressure, of the liquid pig iron and the slag at 1.500 degrees Centigrade; b - the unavoidable impacts caused by the blast-furnace gun that is activated to seal the refractory concrete of the iron notches after the runs and that, the most delicately they are operated, they always hit the concrete of the iron notches; c - the vibrations and impacts caused by the drill that tears the concrete of the iron notch core to allow the run to take place.
For the aforesaid reasons, it is noted that the iron notches are extremely important areas due to their work and to the blast furnace security and, thus, they need constant maintenance with the production being interrupted. In other words, this means that such area needs new techniques that ensure the security and that decrease the number of stopped hours for maintenance.
The concrete that usually constitutes the core of the iron notch - this concrete is perforated by the drill at every run and replaced by the blastfurnace gun, at every run - lasts about twenty-one days, which is the time span between the programmed halts for maintenances, whereas the stopped time for the other pieces of equipment maintenance is used for mending the iron notch core that must be carried out when the blast furnace is empty and turned off.
The situation is more serious and takes longer when the whole iron notch has to be remade, which happens in about two hundred days after the blast furnace initial work, as the whole refractory structure of the iron notch must be torn down and replaced, a task that must be performed under extremely uneasy physical conditions due to the temperatures and position of the workers, because of the local conditions, literally "the furnace mouth".
The Figures 1 through 4 illustrate the State of the Art of the operation and maintenance of the iron notches.
In Figure 1 , we have a schematic frontal view of the external wall section of the blast furnace basis where the iron notch (1) is seen, which is an interruption of the metallic furnace shell (4) and of its refractory setup, also called "bonnet", which is filled with refractory mass (3), and the refractory core (2) of the iron notch, the place which is perforated for allowing the emptying of the blast furnace and, after its occurrence, it is concreted again.
Figure 2 is a schematic side cut of the same area shown in the frontal view in Figure 1, where one can see the core (2) of the iron notch (1), the iron notch (1), the refractory mass (3) that fills it, the metallic furnace shell (4) of the blast furnace and the inner refractories (5) of the blast furnaces and the concrete placement auxiliary panel (9) that works as a provisory support for the concrete placement of the iron notch (1) and that, when the blast furnace starts to operate, it gets fused; one can also see the A-B arrow that indicates the level the liquid pig iron reaches inside the blast furnace up to the moment of being emptied, when the core (2) of the iron notch (1) is perforated by the drill.
It is seen in Figures 1 and 2 that the State of the Art consists of concreting with the support of the auxiliary concrete placement panel (9) the whole area of the iron notch (1) with the refractory and, at each run,. perforating with the drill and reconstructing the core (2) of the iron notch (1) with the blast-furnace gun, with the consequent production losses pointed out above.
Figure 3 is a schematic side view of the structures shown in Figures 1 and 2 and it illustrates the emptying operations of the core (2) of the iron notch (1) with the drill (6); it also shows the inner refractories (5), .the refractory mass (3) that fills the iron notch (1) and the metallic furnace shell (4) to stand out the sealing operation through the refractory concrete which is carried out by the blast-furnace gun (7), with the bell, standing out the angle with which both the drill (6) - shown in Figure 3 - and the barrel (7) make the iron notch (1) from the horizontal line C-D, which is of 12 degrees, for the particular case of the blast furnace the object of this patent has been developed, but that may widely vary for more or less.
Advances in the State of the Art brought by the "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT", object of this patent.
The object of this patent advances the State of the Art of the maintenance and operation of the iron notches in the blast furnaces for the following reasons:
1st - It decreases the number of stopped hours for maintenance as the iron notch (1) concrete replacement with its use has a useful life span which is four times longer than that obtained by the conventional concrete placement, which uses an auxiliary concrete placement panel (9), making its concrete placement life span increase from an average of 200 days to around 800 days.
2nd - It increases the duration of the iron notch (1) core (2) as the place of contact of the drill (6) and the blast-furnace gun (7) with it, makes with the blast furnace metallic furnace shell (4), from its upper part downwards, the same angle of 12 degrees with which the drill (6) and the blast-furnace gun
(7), thus making these two pieces of equipment to contact it with a straight angle, which lengthens its useful lifespan to about 40 days, almost twice the one gotten by the State of the Art; this increase in the useful lifespan of the iron notch (1) core (2) brings economic gains for the decrease of the number of stopped hours for maintenance, workforce and materials.
3rd - It produces a firmer and safer iron notch (1) and iron notch (1) core (2), which highly increases the security factor of the blast furnace.
Description and illustration of the work of the object of this patent, "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT".
Figure 5 shows the rack (10) with a diagonal view, evidencing its depth and the particularities of its construction; it is built with steel plate, with measures that are compatible with the iron notch (1) and it has shelves (11), holes (13), only with some of them being addressed with the necessary number to its understanding, and the pillars (12).
Figure 6 is a side view of the rack (10) to show the angle that its frontal part makes with the regular one over the ground, represented by the straight E-F, whose vertex is found in the upper part of the rack (10).
Figure 7 is a diagonal view of the auxiliary removable plate (14), with its windows (15), bucket (16) and the angular bend (17).
Figure 8 is a side view of the auxiliary removable plate (14), indicating the bucket (16) and the angular bend (17).
Figure 9 is a side view to address the relations between the blast furnace metallic furnace shell (4), its inner refractories (5), the iron notch (1), and the kit, set up , formed by the rack (10) and the auxiliary removable plate (14) of which the bucket (16) is part.
Figure 10 is a frontal view of the kit composed of the rack (10) and the auxiliary removable plate (14), which stands out, for understanding purposes as it will be described next, the bucket (16) and the windows (15).
Figure 11 is a schematic view, with a side cut, of the pieces of equipment belonging to the blast furnace and of those involved with the object of this patent; we see in it, the blast furnace metallic furnace shell (4), the iron notch (1), the auxiliary removable plate (14), the rack (10) shelves (11), the sealing plates (17) and the refractory concrete (18) after its placement in the bucket (16).
Work of the "RACK AND AUXILIARY REMOVABLE PLATE FOR REFRACTORY CONCRETE PLACEMENT".
As it was described previously, the set formed by the rack (10) and the auxiliary removable plate (14) aims the safe and durable concrete placement of the iron notch (1) that constitutes a piece of equipment that gets worn and requires a periodical maintenance.
The object of this patent is an innovative device of which a part, the rack (10) comes to integrate the concrete of the iron notch (1), giving it the concrete placement perfection and a long duration, and the other, the auxiliary removable plate (14) that enables its fast and safe concrete placement, making the external area of the concrete placement (3) of the iron notch (1) be in such an angle with the blast furnace metallic furnace shell (4) that the drill (6) and the blast-furnace gun (7) reach it at a straight angle, for a better and safer operation.
Thus, once the rack (10) is correctly positioned in the iron notch (1), the auxiliary removable plate (14) is fixed in its frontal part anyhow, such as weld nuggets, wedges and lifting eye, temporary settle "L" bars and the refractory concrete is thrown into the interior of the bucket (16) and goes down gravitationally up to the lower part of the rack (10); as it goes down this can be observed through the windows (15), which also allow the introduction of the vibratory element used for compacting the concrete placement.
As the refractory concrete thrown into the bucket (16) fills the rack (10), from its upper to its lower part, the tentative metallic pieces, called sealing plates (19) as shown in Figure 11 , are held by weld nuggets in the front area of the windows (15).
Due to the high local temperature and to the used refractory concrete chemical composition, it gets dry quickly and takes the shape of the rack (10) released elements and the auxiliary removable plate (14) is removed, leaving the iron notch (1) surface at an angle with the metallic furnace shell (4) that allows an octagonal attack, both by the drill (6) and by the blast-furnace gun (7), which brings additional advantages to the iron notch (1) core (2) duration, and therefore, advantages due to the decrease of the stopped time and the increase of the work security.